Method for producing cellulose acylate film

ABSTRACT

A method for producing a cellulose acylate film is disclosed. The method comprises the steps of, casting dope containing cellulose acylate on a surface of a metal support, peeling off a web formed by casting the dope from the metal support, contacting surface of the web which has been contacted with the surface of the metal support, with a first roller just after the peeling off of the web from the metal support surface, consequently, contacting the surface of the web which has been exposed to air on the metal support, with a second roller, and drying the peeled web.

FIELD OF THE INVENTION

[0001] This invention relates to a method for producing a celluloseacylate film by a solution-casting method.

BACKGROUND OF THE INVENTION

[0002] Cellulose acylate film is usually produced by a solution-castingmethod. By the solution-casting method, a solution of cellulose acylate,hereinafter referred to as a dope, is poured onto an endless metalsupport having a mirror plane through a die arranged upward the supportso as to evaporate the solvent of the dope from the poured layer of thedope. The layer of the dope from which the solvent is evaporated isreferred to as a web. The web, is peeled off from the metal support by apeeling roller when the remaining amount of the solvent is attained at aprescribed amount. Then the web is dried while the web is transported bya roller or a tenter to produce the cellulose acylate film.

[0003] In the solution-casting film producing method, the production wasusually performed at a transportation speed of not more than 40 m/min.Recently, however, the demand for the cellulose acylate film isconsiderably increased. Accordingly, raising in the production speed orthe transportation speed is strongly required to raise the supplyingamount of the film.

[0004] However, it has been found that serious problems are raised onthe surface structure and the flatness of the film. In the usualproduction performed with the transportation speed of not more than 40m/min., the web has been peeled off in a state having a remainingsolvent content of not more than 40%. It has been found by the inventorsthat the peeling ability of the web is considerably degraded when theremaining solvent content exceeds 40%, but improved again when thesolvent content is increased over a certain value. It has been alsofound that the problem of peeling ability has related to not only theremaining solvent content but also some factors such as the differencebetween the temperature at the peeling time and that after the peelingand the surface properties of the roller to be firstly contacted to theweb just after the peeling. This invention is attained based on such theknowledge.

[0005] The object of the invention is to provide a method for producinga cellulose acylate film by which the cellulose acylate film excellentin the flatness and the surface quality with a little curing, wrinkle,unevenness, and defect caused by pressure, can be produced even when thetransportation speed is accelerated. The web can be easily peeled offfrom the metal support and the peeled web can be stably transported anddried by the method according to the invention.

SUMMARY OF THE INVENTION

[0006] The invention and embodiments are described below.

[0007] A method for producing a cellulose acylate film comprising thesteps of

[0008] casting dope containing cellulose acylate and solvent on asurface of a metal support,

[0009] peeling off a web formed by casting the dope from the metalsupport, and

[0010] drying the peeled web,

[0011] wherein remaining content of the solvent in the web when the webis peeled off is within the range of from 70 to 120%,

[0012] contacting surface of the web with a first roller just after thepeeling off of the web from the metal support surface, consequently,

[0013] surface temperature of the first roller Tr is controlled so thatthe relation of the Tr and the surface temperature of the metal supportat the time of peeling Tb is (Tr - Tb)= 50° C., and

[0014] surface roughness R_(max) of the first roller is not more than1.0 μm.

[0015] A method for producing a cellulose acylate film mentioned abovewherein the web is contacted to the first roller within 5 seconds afterpeeled from the metal support.

[0016] A method for producing a cellulose acylate film mentioned abovewherein transportation speed of the web is preferably within the rangeof from 40 m/min. to 120 m/min.

[0017] A method for producing a cellulose acylate film mentioned abovewherein surface temperature of the first roller is gradually decreasedfrom central portion to both end of the roller along longitudinaldirection of the roller.

[0018] A method for producing a cellulose acylate film mentioned abovewherein the web comes into contact with the first roller on the surfaceof the web which has been exposed to air on the metal support.

[0019] A method for producing a cellulose acylate film mentioned abovewherein the web comes into contact with the first roller on the surfaceof the web which has been contacted with the metal support, andconsequently a second roller on the surface of the web which has beenexposed to air on the metal support.

[0020] A method for producing a cellulose acylate film mentioned abovewherein diameter of the first roller is gradually decreased from bothend to the central portion of the roller along the longitudinaldirection of the roller.

[0021] A method for producing a cellulose acylate film mentioned abovewherein diameter of the first roller is gradually increased from bothend to the central portion of the roller along the longitudinaldirection of the roller.

[0022] A method for producing a cellulose acylate film mentioned abovewherein the first roller is a nipping roller.

[0023] A method for producing a cellulose acylate film mentioned abovewherein each both edges of the web after peeling off from metal supportcomes contact with two rollers, so that the angles of the axis of eachof the roller with the direction perpendicular to the transportationdirection of the web are θ and (180° - θ′), respectively, and θ and θ′are each satisfy the condition of

[0024]  θ>0° and θ<90°.

[0025]

[0026] A method for producing a cellulose acylate film mentioned abovewherein position of the first roller is varied so that the angle formedby the web with the metal support keeps constant at a point where theweb is peeled off from the metal support.

[0027] A method for producing a cellulose acylate film mentioned abovewherein position of the first roller is varied according to remainingsolvent content or surface temperature of the web at the time of peelingof the web from the metal support.

[0028] A method for producing a cellulose acylate film mentioned abovewherein air is blown with a flow rate of not less than 20 m/second tothe surface of the web at side which has been contacted to the metalsupport after peeling off from the metal support.

[0029] A method for producing a cellulose acylate film mentioned abovewherein the web comes into contact with the first roller and then asecond roller, wrapping angle of the web with the first roller beingvaried by changing position of the second roller corresponding tocontent of remaining solvent or surface temperature of the web at aposition where the web is peeled off from the metal support. In one ofthe embodiment, the diameter of the first roller is preferably decreasedfrom both ends to the center of the roller.

[0030] In the other embodiment, the diameter of the second roller ispreferably increased from both ends to the center of the roller.

[0031] A method for producing a cellulose acylate film by asolution-casting method comprising the steps of

[0032] peeling off a web form a metal support,

[0033] firstly passing the web between a pair of nipping rollers, and

[0034] drying the web.

[0035] A method for producing a cellulose acylate film by asolution-casting method comprising the steps of

[0036] peeling off a web from a metal support,

[0037] touching two small rollers to each the both edges of the surfaceof the web, which has been contacted to the metal support, just afterthe peeling off of the web from the metal support surface, so that theangles of the axis of each of the roller with the surface of the web areθ and (180° - θ′), respectively, and θ and θ′ are each satisfy thecondition of

θ>0° and θ′<90°,

[0038] thereafter, contacting the surface of the web which has beenexposed to air on the metal support, to the first roller, and

[0039] drying the web.

[0040] A method for producing a cellulose acylate film by asolution-casting method comprising the steps of

[0041] peeling off a web from a metal support,

[0042] contacting the web to a first roller, the position of which isvaried corresponding to the content of remaining solvent in the web at atime just after the web is peeled or the surface temperature of the webat the time of peeling, and

[0043] drying the web.

[0044] A method for producing a cellulose acylate film by asolution-casting method comprising the steps of

[0045] peeling off a web from a metal support,

[0046] vertically blowing air at a speed of not less than 20 m/secondonto the surface of the web, which has been contacted with the metalsupport, through a slit arranged at a position upward the web,

[0047] contacting the face of the web which has been exposed to air onthe metal support, to the first roller, and drying the web.

[0048] (8) The distribution in the across direction of the web of theflow rate of air vertically blown to the web through the slit ispreferably gradually increased from the center to the both ends of theweb.

[0049] A method for producing a cellulose acylate film by asolution-casting method comprising the steps of

[0050] peeling off a web from a metal support,

[0051] contacting the web to a first roller,

[0052] then contacting the web to a second roller, and

[0053] drying the web,

[0054] wherein the wrapping angle of the web to the first roller isvaried corresponding to the content of solvent remaining in the web atthe time of peeling by varying the position of the second roller.

[0055] The surface temperature of the surface of the first rollerpreferably has a distribution in which the temperature is graduallydecreased from the central portion in the longitudinal direction of theroller to the both ends of the roller.

[0056] A method for producing a cellulose acylate film by asolution-casting method comprising the steps of

[0057] peeling off a web from a metal support,

[0058] contacting the web to a first roller, and

[0059] drying the web,

[0060] wherein the surface temperature of the first roller Tr iscontrolled so that the relation of the Tr and the surface temperature ofthe metal support at the time of peeling Tb is (Tr - Tb)= 50° C.

[0061] The surface temperature Tr of the roller preferably has adistribution in which the temperature is gradually decreased from thecentral portion in the longitude direction of the roller to the bothends of the roller.

[0062] In the method for producing a cellulose acylate film the surfaceroughness Ra of the roller to which the web is firstly contacted ispreferably Ra= 1.0 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0063]FIG. 1 is a schematic drawing of a solution-casting film producingapparatus.

[0064]FIG. 2 is a schematic drawing of a part of a solution-casting filmproducing apparatus showing the relation between the first roller to befirstly contacted to the web and the second roller.

[0065]FIG. 3 is a sketch of the roller to be firstly contacted to theweb, in which the diameter at the central portion in the longitudinaldirection is smaller than the diameter at the both ends of the roller.

[0066]FIG. 4 is a sketch of the roller to be secondarily contacted tothe web, in which the diameter at the central portion in thelongitudinal direction is larger than the diameter at the both ends ofthe roller.

[0067]FIG. 5 is a schematic drawing of a part of a solution-casting filmproducing apparatus having a pair of nipping rollers as a peelingroller.

[0068]FIG. 6 is a schematic drawing of a part of a solution-casting filmproducing apparatus having two small rollers each forming angles θ and(180° - θ′), respectively.

[0069]FIG. 7 is a schematic drawing of a part of a solution-casting filmproducing apparatus having a peeling roller capable of changing theposition thereof.

[0070]FIG. 8 is a schematic drawing of a part of a solution-casting filmproducing apparatus having a movable second roller.

DETAILED DESCRIPTION OF THE INVENTION

[0071] The production method of cellulose acylate film according to theinvention comprises a step of casting a dope containing celluloseacylate onto a metal support; a step of peeling off a cellulose acylateweb formed by pouring the dope from the metal support; and a step ofdrying the peeled web.

[0072] The peeling ability of the web is considerably improved when theremaining content of the solvent in the web is within the range of from70 to 120%. Furthermore, the peeling ability of the web and the surfaceproperty of the film are raised when the web is firstly contacted to thefirst roller just after peeled off form the metal support and thesurface temperature Tr of the first roller and the surface temperatureTb of the metal support at the time of the peeling satisfy the equationof (Tr - Tb)= 50° C., and the surface roughness R_(max) of the firstroller is not more than 1.0 μm. The temperature can be controlled byadjusting the room temperature, jacket warming water roll, inductionheating roll and so on.

[0073] The Tr can be measured by touching a touching type thermometer tothe surface of the first roller and the Tb can be measured by touching atouching type thermometer to the surface of the metal support at thepeeling position. When the temperature at the surface of the firstroller or the surface of the metal support at the peeling position has adistribution, the temperature is measured ten points with about uniforminterval in the direction perpendicular to the transportation directionand Tr and Tb are each defined by the average values thus obtained.

[0074] It is more preferable that 15° C.= (Tr - Tb)< 30° C. Tr is morepreferably within the range of from 10° C. to 70° C., and Tb is morepreferably within the range of from 0° C. to 50° C.

[0075] The R_(max) is measured by the method of measuring of “Ry”described in JIS B 0601-1994. Rmax is the difference from the deepestbottom to the highest peak in the predetermined range, for example, 25mm, of the cross section curve, which is the outline of the crosssection figure appeared when the film is cut along with a plane at rightangle to the film plane. The remaining solvent content is describedlater. R_(max) is preferably not more than 0.8 μm, more preferably notmore than 0.3 μm.

[0076] It is preferable that the web is contacted to the first rollerwithin 5 seconds, more preferably within 3 seconds, after peeled fromthe metal support. When the web is contacted to the second roller aftercontacting to the first roller, it is preferable to contact to thesecond roller within 5 seconds after contacting to the first roller.

[0077] The transportation speed of the web is preferably within therange of from 40 m/min. to 110 m/min., more preferably from 50 m/min. to100 m/min.

[0078] The first roller may be either one to be contacted to the surfaceof the web opposite to the side which has been contacted with the metalsupport or one to be contacted to the side of the web which has beencontacted to the metal support. When the first roller is a roller to becontacted to the surface of the web which has been contacted with themetal support, it is preferable that the second roller is a roller to becontacted to the surface of the web which is opposite to the surfacewhich has been contacted with the metal support.

[0079] It is preferable to change the position of the first roller sothat the angle formed by the web with the metal support is constant. Forexample, it is preferable to provide a tension measuring device and tochange the position of the first roller according to the measuringresult by the tension measuring device.

[0080] In another embodiment, it is allowed that the position of thefirst roller is changed according to the remaining solvent content orthe surface temperature of the web at the time of peeling of the webfrom the metal support, or the wrapping angle of the web on the firstroller is changed by changing the position of the second rolleraccording to the remaining solvent content or the surface temperature ofthe web at the time of peeling of the web from the metal support. Forexample, the more the residual solvent content becomes, the lower thefirst roller preferably varied its position, and the less the residualsolvent content becomes, the higher the first roller preferably variedits position.

[0081] The cellulose acylate relating to the invention is one derived bysubstituting hydroxy groups of cellulose by an acetyl groups, or amixture of an acetyl group and a propionyl group, that of an acetylgroup and a butyryl group, or that of an acetyl group, propionyl groupand a butyryl group. The substitution degree of the acyl group to thewhole hydroxy group of cellulose is preferably within the range of from2.5 to 3.0. It is preferable in the mixture of the acyl group that theacetyl group accounts for not lee than 50% of the total substitutiondegree.

[0082] The dope relating to the invention is prepared by dissolvingcellulose acylate by an organic solvent capable of dissolving thecellulose acylate. For example, methylene chloride, methyl acetate,acetone, 1,3-dioxolan, and 1,4-dioxane are preferably usable even thoughones capable of dissolving the cellulose acylate can be used without anylimitation. Casting at a high speed can be realized by additionallyadding anther organic solvent such as an alcohol having from 1 to 4carbon atoms or cyclohexane in an amount of from 1 to 30% by weight. Anusual dissolving method under a pressure near the ordinary pressure, thedissolving methods described in Japanese Patent Publication Open toPublic Inspection, hereinafter referred to as JP O.P.I., Nos. 9-95544,9-95557, and 9-95538, and the high pressure dissolving method describedin JP O.P.I. No. 11-21379, can be applied for dissolving celluloseacylate. Among them one capable of easily dissolving the celluloseacylate may be applied.

[0083] The solution-casting film producing method relating to theinvention is described below according to FIG. 1. FIG. 1 is a schematicdrawing a solution-casting film producing apparatus. A dope issatisfactorily filtered and defoamed according to necessity, andtransported through a precise pump (not shown in the drawing) to a die1. The die 1 may be either a coat hunger type die or a T-type die. Thedope is poured through the die 1 onto a circulating endless metal beltsupport 3 having a polished mirror surface or a rotating metal drumsupport having a chromium plated smooth surface (not shown in thedrawing) so as to form a dope layer 2 having a prescribed thickness. Thedope layer 2 is heated from the air side and/or the metal support sideto evaporate the solvent satisfactorily for forming a web 2′ capable ofbeing peeled off from the support in the period of one round of thesupport. The web 2′ is peeled off from the support just before one roundof the support. The web 2′ is dried by exposing both sides thereof toair or air containing a large amount of nitrogen gas while the web istransported by a peeling roller 4, the roller firstly contacted to theweb, and the second roller 5, and passed through drying device 7 havinga group of rollers 6, or through a tenter (not shown in the drawing) inwhich the both edges of the web are clipped. The dried web 2′ is windedup in a form of a film 2″. Both of the drying device having the rollergroup 6 and the tenter may be used d for drying the web. The amount ofthe solvent remained in the film 2″ at the time of finish of the dryingis within the range of from 0.01 to 3.0% by weight and usually not morethan 2.0% by weight.

[0084] The content of the remaining solvent is defined by the followingequation:

Remaining solvent content (%)= {(M - N)/N}×100

[0085] In the above, M is the weight of the web at an arbitrary time andN is the weight of the web after dried at 110° C. for 3 hours.

[0086] More preferable embodiments of the invention are described belowaccording to the drawings.

[0087]FIG. 2 is a schematic drawing of a part of a solution-casting filmproducing apparatus showing the relation between the roller to befirstly contacted with the web and the second roller. FIG. 3 shows asketch of the first roller to be firstly contacted to the web, of whichdiameter at the central portion is smaller than that at the both endsthereof. FIG. 4 shows a sketch of the second roller to be secondarycontacted to the web, of which diameter at the central portion is largerthan that at the both ends thereof. The invention is characterized inthat the surface of the web which has been contacted with the metalsupport is firstly contacted to the first roller 14 and the surface ofthe web which has been exposed to air on the metal support is secondarycontacted to the roller 15. The first roller 14 is provided to stablyperform the peeling.

[0088] Usually, the web 2′ tends to curl at the both edges thereof tothe metal support side after peeled off from the support, and is easilyfolded at the entrance of the next roller. Such the folding at the bothedges of the peeled web can be prevented by the use of a roller such asthat shown in FIG. 4 of which diameter is decreased from the both endsto the central portion thereof as the first roller 14 so as to stabilizethe transportation of the web in the process hereafter. Moreover, thetransportation of the web can be further stabilized by the use of aroller such as that shown in FIG. 4 of which diameter is increased fromthe both ends to the central portion of the roller as the second roller15.

[0089]FIG. 5 is a schematic drawing of a part of a solution-casting filmproducing apparatus having a pair of nipping rollers as a peelingroller. The position at which the web 2′ is peeled off from the supportcan be constant by the use of the pair of nipping rollers 24 as theroller to be firstly contacted to the web 2′ just after the peelingthereof or the peeling roller. Thus a film having a high flatnesswithout formation of an across unevenness caused by fluctuation of thepeeling position can be produced. The pressure of the nipping roller ispreferably within the range of from 1 to 100 kPa, more preferably from 1to 50 kPa. The upper roller of the nipping rollers may be separate totwo rollers having a length shorter than half of length of the lowerroller to nip each of the both edges of the web, even though the upperroller has a length similar to that of the lower roller.

[0090]FIG. 6 is a schematic drawing a solution-casting film producingapparatus having two small rollers each provided to form an angle of θand (180° - θ′) with the surface of the web 2′. In the apparatus, thetwo small rollers 34 which are each arranged so as to form an angle of θand (180° - θ′) with the surface of the web, respectively, are touchedto both edges of the surface of the web which has been contacted withthe surface of the metal support in the state as shown in the figure.The peeling position of the web is stabilized by the presence of the twosmall rollers. The two small rollers each may form any angle with thesurface of the web. It is preferable that the web is contacted to thefirst roller (not shown in the drawing) on the opposite side to a sidewhich has been contacted to the metal support (i.e., a side which hasbeen exposed to air on the metal support) at a position as near aspossible the position at which the small rollers are touch to the web.The peeling position can be stabilized by making the angle θ to 10 to80° and θ′ to 100 to 170°, preferably from 15 to 50° and from 130 to165°, preferably.

[0091] The length of the small roller is preferably smaller than thewidth of the web, usually preferably from 500 mm to 600 mm. The diameterof the small roller is preferably from 80 to 200 mm.

[0092]FIG. 7 is a schematic drawing of a part of a solution-casting filmproducing apparatus having a peeling roller which can be changed in theposition thereof. In the apparatus the position of the roller 44 to befirstly contacted to the surface of the web which has been exposed toair on the metal support can be changed corresponding to the content ofremaining solvent at the time of peeling or the surface temperature ofthe web at the time of peeling. Therefore, the film can be produced by astable peeling condition by the change of the roller position even whenthe composition of the dope such as the kind of the solvent or theconcentration of the dope, the casting speed or the drying condition ischanged.

[0093] Another preferable embodiment of the invention is a filmproducing method by which air is vertically blown with a flow rate ofnot less than 20 m/second, preferably from 20 to 30 m/second onto thepeeled web through a slit arranged upward the web (not shown in thedrawing) at a position before the peeling roller. The blowing throughthe slit either may be applied to the whole wide of the web or only bothof the edge portions of the web. It is also preferred that air blownthrough the slit is gradually increased at the central portion in theacross direction of the web. Such the means is performed to compensatethe difference of the amount of remained solvent between the portion ofthe web, usually the drying of the web is late some degree at thecentral portion of the web. By this means, the difference of theremaining solvent amount in the across direction of the web can beunitized as soon as possible. Any device can be used for blowing air aslong as the device can uniformly blow air.

[0094] The air stream is not limited to the air blown through a slit,and the device to blow air is not limited to the slit or nozzle.

[0095]FIG. 8 is a schematic drawing a part of a solution-casting filmproducing apparatus having a movable second roller. In the apparatus,the wrapping angle of the web 2′ with the first roller 54 is changedcorresponding to the content of remaining solvent by changing positionof the second roller 55 to stabilize the peeling force. It is preferablethat the first roller 54 is driven to further stabilize the peelingforce. However, large torque cannot be applied to the web since the webcontaining a considerably high content of remaining solvent is verysoft. Accordingly, the driven roller may be given a speed change of from1.001 to 1.00. It is also preferable that the surface temperature of thefirst roller is gradually decreased from the central portion to the bothend of the roller along the longitudinal direction of the roller.

[0096] The wrapping angle is an angle formed by the two lines eachconnecting the contacting points of the web to the roller and thecentral portion of the roller.

[0097] A film 2″ excellent in the flatness can be produced bycontrolling surface temperature Tr of the roller 4 to which the web isfirstly contacted as shown in FIG. 1 and the temperature Tb of the metalsupport 3 on which the web is contacted, at the peeling point so thatthe relation of them is Tr - Tb= 50° C. The contactness of the firstroller 4 and the web 2′ is raised and the peeling ability of the web isimproved without degradation of the flatness under such the condition.The difference of the temperature Tr - Tb is preferably from 15 to 30°C. The flatness of the film can be further improved by giving atemperature distribution to the surface temperature Tr of the firstroller in which the surface temperature Tr is gradually decreased fromthe central portion to the both end of the roller along the longitudinaldirection of the roller. The difference of the temperature at thecentral portion of the roller and that at the end of the roller ispreferably not more than 15° C.

[0098] In another preferable embodiment of the invention, the flatnessis further improved and the scratch caused by the slip of web 2′ on theroller can be prevented by making the surface roughness Ra of the rollerto be firstly contacted to the peeled web such as 4, 14, 24, 44, and 45in the drawings to Ra= 1.0 μm.

EXAMPLE

[0099] The invention is described below according to examples.

[0100] [Preparation of dope and production of film]

[0101] In a dissolving vessel, 100 parts by weight of cellulosetriacetate was dissolved in 400 parts by weight of methylene chloride,80 parts by weight of ethanol, and 15 parts by weight of triphenylphosphate by stirring for 5 hours. The solution was filtered by a filterpress to prepare a dope. The dope was transported to a coat hunger diethrough a pressing quantitative pump and poured on a metal support toform a dope layer so that the dry thickness was 120 μm. The solventswere evaporated on the metal support. The web was peeled off when thecontent of remaining solvent reached at the prescribed value and driedat a temperature of from 80 to 130° C. Thus a film was prepared. In thefollowing examples, the web peeled from the metal support was firstlycontacted to the first roller, the surface roughness of the first rollerR_(max) was 1.0 μm, the remaining solvent content at the time of peelingthe cellulose acylate web from the metal support was 100% (exceptingExamples 6, 7, 10, and 11, and Comparative Example 1), the surfacetemperature of the first roller Tr was uniformly 30° C. and the surfacetemperature of the metal support Tb at the peeling of the web wasuniformly 10° C. (excepting Comparative example 2).

[0102] [Evaluation method]

[0103] <Peeling ability>

[0104] A standard peeling point was set on the metal support and thefluctuation of the peeling point of the web from the metal support wasmeasured and classified into six ranks according to the following norms.The remaining content of the solvent at the time of peeling was 100% byweight.

[0105] A: Fluctuation not more than was ±20 mm.

[0106] B: Fluctuation was more than 20 mm and not more than 35 mm.

[0107] C: Fluctuation was more than 35 mm and not more than 50 mm.

[0108] D: Fluctuation was more than 50 mm and not more than 75 mm.

[0109] E: Fluctuation was more than 75 mm and not more than 100 mm.

[0110] F: Fluctuation was more than 100 mm.

[0111] <Surface quality of film>

[0112] A film sample having a size of 1 m by whole width of the film wassampled from the dried film. The sample was laid on a flat table whichwas lighted by three fluorescent light tubes arranged in parallel upwardthe table at a height of 2 m. The state of the film surface was visuallyobserved and classified in to the following ranks according to the stateof the reflected image of the fluorescent light tubes on the samplesurface.

[0113] A: The reflex image of the fluorescent light was straight and nowrinkle was observed.

[0114] B: The reflex image of the fluorescent light was almost straightand wrinkles were observed little.

[0115] C: The reflex image of the fluorescent light was slightly curvedand wrinkles were observed a little.

[0116] D: The reflex image of the fluorescent light was partially curvedand wrinkles were observed some degree.

[0117] E: The reflex image of the fluorescent light was zigzag in somedegree and wrinkles were appeared.

[0118] F: The reflex image of the fluorescent light was irregular andmany wrinkles were observed.

Comparative example 1

[0119] As shown in FIG. 1, the surface of a web opposite to the surfacewhich had been contacted with the metal support was contacted to thefirst roller as the peeling roller just after the peeling of the web,and transported and dried. The fluctuation of the peeling point wasmeasured in the course of the film preparation, and the surface qualityof the film was evaluated after the drying. The surface roughness of thefirst roller was 1.0 μm in R_(max), and the content of the solventremained in the web at the time of peeling the cellulose acylate webfrom the metal support was 50% by weight. The surface temperature Tr ofthe first roller and that Tb of the metal support at the time of peelingwere each uniformly 30° C. and 10° C., respectively.

Comparative example 2

[0120] A sample of film was prepared under the conditions of the surfaceroughness R_(max) of the first roller was 1.0 μm, and the content of thesolvent remained in the web at the time of peeling the cellulose acylateweb from the metal support was 100% by weight. The surface temperatureTr of the first roller and that Tb of the metal support at the time ofpeeling were each uniformly 70° C. and 10° C., respectively. Theconditions other than the above were the same as in Comparative example1.

Example 1

[0121] A web having a remaining solvent content of 100% by weight waspeeled from the metal support. The surface of the web which has beencontacted with the surface of the metal support was contacted to thefirst roller. Then the web was contacted to the second roller so as tobe transported, and dried in the drying device.

Example 2

[0122] A film was prepared in the same manner as in Example 1 exceptthat the first roller was replaced by a roller which had a diametersmaller at the central portion thereof than that at the both ends of theroller.

Example 3

[0123] A film was prepared in the same manner as in Example 2 exceptthat the first roller was replaced by a roller which had a diameterlarger at the central portion thereof than that at the both ends of theroller.

Example 4

[0124] A web having a remaining solvent content of 100% was peeled andfirstly contacted to a pair of nipping rollers as shown in FIG. 5applying a nipping pressure of from 5 to 10 kPa, and transported by thenipping roller applying a nipping pressure of from 5 to 10 kPa and driedin the drying device.

Example 5

[0125] A web a remaining solvent content of 100% was peeled. Just afterthe peeling, two inclined small rollers each forming an angle θ of 20°and an angle θ′ of 160° C. with the surface of the web were touched tothe booth edges of the metal support side surface of the web. Just afterthat, the first roller was touched to the air side of the web surface totransport the web and the web was dried by a drying device.

Example 6

[0126] A web a remaining solvent content of 105% was peeled andcontacted to the first roller arranged at the ordinary position. The webwas transported and dried by a drying device.

Example 7

[0127] A film was prepared in the same manner as in Example 6 exceptthat the remaining solvent amount in the web was 95% and the position ofthe first roller was moved upward by 100 mm.

Example 8

[0128] A web was peeled. Just after that, air was vertically blownuniformly through a slit at a flow rate of 20 m/second to the metalsupport side of the web. Then the air side of the web was contacted tothe first roller. The web was transported and dried.

Example 9

[0129] A film was prepared in the same manner as in Example 8 exceptthat the distribution of the air amount was changed so that the airamount was reduced by 5% from the central portion to the edge portion ofthe web.

Example 10

[0130] A web having a remaining solvent content of 105% was peeled fromthe metal support. Just after the peeling, the web was contacted to thefirst roller at a fixed position. Then the web was contacted to thesecond roller capable of being changed the position thereof so thewrapping angle of the web was 60°, and transported and dried.

Example 11

[0131] A film was prepared in the same manner as in Example 10 exceptthat the remaining solvent content of the web was varied to 95% and thewrapping angle was changed to 78° by moving downward the position of thesecond roller by 100 mm.

Example 12

[0132] A film was prepared using the apparatus shown in FIG. 1.

Example 13

[0133] A film was prepared in the same manner as in Example 12 exceptthat the roller was replaced by a roller having a surface temperaturegradient so that the temperature at central portion in the longitudinaldirection was 35° C. and the temperature at the both ends of the rollerwas 25° C.

[0134] Evaluation results of the foregoing Examples and Comparativeexamples are shown in table 1. TABLE 1 Peeling Surface ability qualityRemarks Example 1 A A Example 2 A A Curl at the edges is a little.Example 3 A A Curl at the edges is a little. Example 4 A A Example 5 A AExample 6 A A Example 7 A A Example 8 A A Example 9 A A Curl at theedges is a little.  Example 10 A A  Example 11 A A  Example 12 A A Example 13 A A Comparative E E  Example 1 Comparative E E  Example 2

[0135] Results

[0136] As is shown in Table 1, the good results are obtained in the allexamples each according to the various embodiments of the invention.

[0137] A method for producing a cellulose acylate film is provided bythe invention, by which the cellulose acylate film excellent in theflatness and the surface quality with a little curing, wrinkle,unevenness, and defect caused by pressure can be produced even when thetransportation speed is accelerated. The web can be easily peeled offfrom the metal support and the peeled web can be stably transported anddried by the method according to the invention.

1. A method for producing a cellulose acylate film comprising the stepsof casting dope containing cellulose acylate and solvent on a surface ofa metal support, peeling off a web formed by casting the dope from themetal support, and drying the peeled web, wherein remaining content ofthe solvent in the web when the web is peeled off is within the range offrom 70 to 120%, contacting surface of the web with a first roller justafter the peeling off of the web from the metal support surface,consequently, surface temperature of the first roller Tr is controlledso that the relation of the Tr and the surface temperature of the metalsupport at the time of peeling Tb is (Tr - Tb)=50° C., and surfaceroughness R_(max) of the first roller is not more than 1.0 μm.
 2. Amethod for producing a cellulose acylate film of claim 1 wherein the webis contacted to the first roller within 5 seconds after peeled from themetal support.
 3. A method for producing a cellulose acylate film ofclaim 1 , wherein transportation speed of the web is within the range offrom 40 m/min. to 120 m/min.
 4. A method for producing a celluloseacylate film of claim 1 , wherein surface temperature of the firstroller is gradually decreased from central portion to both end of theroller along longitudinal direction of the roller.
 5. A method forproducing a cellulose acylate film of claim 1 , wherein the web comesinto contact with the first roller on the surface of the web which hasbeen exposed to air on the metal support.
 6. A method for producing acellulose acylate film of claim 1 , wherein the web comes into contactwith the first roller on the surface of the web which has been contactedwith the metal support, and consequently a second roller on the surfaceof the web which has been exposed to air on the metal support.
 7. Amethod for producing a cellulose acylate film of claim 6 whereindiameter of the first roller is gradually decreased from both end to thecentral portion of the roller along the longitudinal direction of theroller.
 8. A method for producing a cellulose acylate film of claim 6wherein diameter of the first roller is gradually increased from bothend to the central portion of the roller along the longitudinaldirection of the roller.
 9. A method for producing a cellulose acylatefilm of claim 1 wherein the first roller is a nipping roller.
 10. Amethod for producing a cellulose acylate film of claim 1 wherein eachboth edges of the web after peeling off from metal support comes contactwith two rollers, so that the angles of the axis of each of the rollerwith the direction perpendicular to the transportation direction of theweb are θ and (180° - θ′), respectively, and θ and θ′ are each satisfythe condition of θ>0° and θ′<90°.
 11. A method for producing a celluloseacylate film of claim 1 wherein position of the first roller is variedso that the angle formed by the web with the metal support keepsconstant at a point where the web is peeled off from the metal support.12. A method for producing a cellulose acylate film of claim 1 whereinposition of the first roller is varied according to remaining solventcontent or surface temperature of the web at the time of peeling of theweb from the metal support.
 13. A method for producing a celluloseacylate film of claim 1 wherein air is blown with a flow rate of notless than 20 m/second to the surface of the web at side which has beencontacted to the metal support after peeling off from the metal support.14. A method for producing a cellulose acylate film of claim 1 whereinthe web comes into contact with the first roller and then a secondroller, wrapping angle of the web with the first roller being varied bychanging position of the second roller corresponding to content ofremaining solvent or surface temperature of the web at a position wherethe web is peeled off from the metal support.